Transmission cover with improved airflow

ABSTRACT

A cover for a transmission having improved airflow path is disclosed. The interior of the cover has a progressively narrowing airflow path to reduce pressure drop through the cover, thereby improving the cooling efficiency of the airflow through the cover. The cover includes a diverter sheltering the air inlet to the cover to prevent air in the cover from exerting outward pressure on the incoming air.

FIELD OF INVENTION

This invention relates generally to a case for a vehicle transmission such as a continuously variable transmission (“CVT”) with an improved airflow path.

BACKGROUND OF THE INVENTION

All-terrain vehicles (“ATVs”) and recreational off-road vehicles (“ROVs”) generally feature CVTs to transmit power from the engine to the wheels. Like other moving parts of the vehicle, transmissions tend to generate heat during use that, if left unchecked, can be harmful to components of the engine. CVTs in particular generate heat due to the belt sides scrubbing against the sides of the sheaves anytime they are engaged and moving. CVTs are conventionally cooled by moving external air into the CVT cover and over the hot components and out of the cover. However, due to the rapid motion within the CVT cover and the intense space constraints in an engine and transmission, proper airflow is not always achieved efficiently. There is a demand in the art for improved, efficient cooling features for engines generally and specifically for CVTs.

SUMMARY OF THE INVENTION

The present invention is directed to a cover or case for a transmission. The transmission can be a CVT or another suitable transmission having a drive shaft and a driven shaft. The cover includes a first hole for accommodating one of the drive shaft or the driven shaft of the transmission and a second hole for accommodating the other one of the drive shaft and driven shaft. The cover has a lateral dimension measured in a direction parallel to the shafts, and a line passing between center points of the first and second holes separates the cover into a first side and a second side. The cover also has an air inlet near the first hole and an air outlet near the second hole. The cover has a deep region near the air inlet, a ramp region adjacent to the deep region, and a shallow region adjacent to the ramp region. The deep region has a larger lateral dimension than the shallow region and the ramp region slopes between the deep region and the shallow region. The deep region, ramp region, and shallow region are on the first side of the cover. Airflow through the cover is directed to pass into the air inlet, over the deep region, ramp region, and shallow region before exiting the cover. The cover also includes a high region between the air outlet and air inlet on the second side of the cover, having a smaller lateral dimension than the shallow region. A portion of the air from the shallow region passes over the high region before joining the incoming airflow at the inlet. The cover also has a ridge between the first and second holes and separating the ramp region and the high region and a diverter between the high region and the air inlet and positioned to prevent air from the high region from exerting pressure on the incoming airflow.

Other embodiments of the present disclosure are directed to a cover for a transmission having a drive gear and a driven gear rotatably coupled. The cover includes a first end configured to accommodate the driven gear, a second end opposite the first end configured to accommodate the drive gear, and a middle section between the first and second ends. The first end, second end, and middle section together form an oval “racetrack” path for airflow. The cover also has an air inlet and an air outlet opposite the air inlet. Air introduced through the air inlet moves around the racetrack path. A portion of the air leaves the cover through the air outlet and a portion of the air cycles around the racetrack path. A first portion of the racetrack path between the air inlet and air outlet is wider near the air inlet and becomes progressively narrower between the air inlet and the air outlet, and a second portion of the airflow path between the air outlet and the air inlet is narrower than a narrowest region of the first portion of the racetrack path. The cover also includes a diverter extending from the second flow path over the air inlet to prevent air from the second portion of the flow path from exerting pressure onto air introduced to the cover through the air inlet.

In still further embodiments, the present disclosure is directed to a transmission including a drive gear, a driven gear, and means for rotatably coupling the drive gear to the driven gear to transmit power from the drive gear to the driven gear. The transmission is held within a cover surrounding the drive gear and driven gear. The cover has an elliptical shape to accommodate the round shape of the drive gear and the driven gear, an air inlet configured to direct air into the cover to cool the drive gear and driven gear, and an air outlet configured to release air from the cover after cooling the drive gear and the driven gear. The cover has a lateral interior dimension measured between interior walls of the cover measured in a direction parallel to the axes of rotation of the drive gear and driven gear. The air inlet and air outlet are positioned to direct the air to circulate around the interior of the cover in a racetrack path defined by the elliptical shape of the cover, the racetrack path having a first segment between the air inlet and air outlet on a first side of the cover and a second segment between the air outlet and the air inlet on a second side of the cover. The lateral dimension of the cover on the first side of the cover is widest at the air inlet, narrowest at the air outlet, and ramps from wide to narrow between the air inlet and air outlet. The lateral dimension of the cover on the second side of the cover is narrower than a narrowest point of the first side of the cover. The cover also has a diverter extending from the second side of the cover over at least a portion of the air inlet to prevent air moving over the second side of the cover from exerting pressure on incoming air in the air inlet.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings.

FIG. 1 is a partially cut-away view of a CVT according to embodiments of the present disclosure.

FIG. 2 is an interior view of a portion of the CVT cover according to embodiments of the present disclosure.

FIG. 3 is an interior view of a portion of the CVT cover according to further embodiments of the present disclosure.

FIGS. 4A-E illustrate CVT cover alternate embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a partially cut-away view of a CVT 100 and a CVT cover 110. The CVT 100 has a driven clutch 101, a drive clutch 102, and a belt 103 between the driven clutch 101 and the drive clutch 102. The drive clutch 102 is coupled to the engine crankshaft (not shown), receives power from the engine, and transmits the power through the belt 103 to the driven clutch 101, and eventually from the driven clutch 101 to the wheels. The drive clutch 102 can have two conical sheaves 104 holding the belt 103 between them. Moving the sheaves 104 toward and away from one another changes the effective gear ratio of the drive and driven clutch system. As the sheaves 104 of the drive clutch 102 move farther apart the belt drops to a lower location on the sheaves 104 and to a higher location on the sheaves of the driven clutch 101. Conversely, as the drive sheaves move closer together, the driven sheaves mover farther apart. Thus, the gear ratios from input to output smoothly change, thereby achieving a continuously variable transmission. Although, all the movement of the belt sides along the sides of the sheaves as the clutches are turning creates heat. The belt can only withstand so much heat before it fails under a load. Aspects of the present invention can also be used with other transmissions and with other engine casing components.

The backside (first portion 116) of CVT cover 110 surrounds the side of the CVT 100 adjacent the engine and transmission and protects the moving parts. The cover 110 also serves as a channel through which air moves to cool the sheaves and belt. The cover includes an air inlet 112 near the drive clutch 102 and an air outlet 114 near the driven clutch 101. The positions of the air inlet 112 and outlet 114 can vary slightly, but preferably the air inlet 112 and outlet 114 are on substantially opposing sides of the cover 110 to permit the air to flow over the components of the CVT 100 and out the other side. The cover 110 is formed of two portions: a first portion 116, and a second portion 118. The two portions 116, 118 are split along a line parallel with the belt and are held together by bolts through bosses 120 around the periphery of the cover 110. The bosses are preferably on the external portion of the CVT cover 110 to allow smoother air flow in the interior of the cover for better cooling. The first portion 116 can be on the engine side and the second portion 118 can be on the wheel side, or vice versa. In the illustrated embodiment, the first side 116, in which the air inlet 112 and air outlet 114 are formed, are both on the engine side of the CVT 100. Depending on the configuration of the CVT 100 and engine, the heat builds up more significantly on the engine side of the CVT 100. However, in a different configuration, the heat may be more concentrated elsewhere, in which cover the air inlet 112 and outlet 114 can be positioned accordingly. The air inlet 112 and outlet 114 are also preferably located where a fan 115 can pull air into the cover. In this case, the fan is convenient to situate on the engine side of the drive clutch sheaves 104. The fan moves air into the cover and towards the outlet 114.

FIG. 2 is an interior view of the first portion 116 of the CVT cover 110 according to embodiments of the present invention. The first portion 116 has two holes 122, 124 to accommodate the shafts of the drive clutch 102 and the driven clutch 101, respectively. The clutches 101, 102 turn clockwise as shown by arrows A. The cover 110 has an inlet end 126 near the inlet 112 and an outlet end 128 near the outlet 114. The cover 110 is generally rounded at the ends 126, 128 and somewhat straight in the middle. In some embodiments the inlet end is slightly smaller than the outlet end 128 because the drive clutch 102 is smaller; however, in other embodiments their relative sizes can vary to accommodate the sizes of the driven clutch 101 and drive clutch 102. The air path through the cover 110 therefore starts at the inlet 112, moves into the inlet end 126 and then along a lower region 130 of the cover 110. Some of the air will rotate around the drive clutch, but the majority of the air is moved into contact with the driven clutch following the rounded interior shape of the outlet end 128 and eventually into the outlet 114 and out of the cover 110.

The lateral dimensions of the cover 110 are defined as a distance between the first portion 116 and second portion 118 in a direction parallel with the shafts that pass through the holes 122, 124. The lateral dimension is also reflected in the distance between the first portion 116 of the cover and the inner faces of the drive and driven clutches 102, 101. These dimensions vary along the airflow path to improve the air pressure at various points along the flow path. The front portion 116 has a deep region 132, followed by a ramp region 134, followed next by a shallow region 136. The deep region 132 has a large lateral dimension to permit air to enter at a relatively lower air pressure when compared to a conventional CVT cover with a uniform lateral dimension. The lateral dimension of the deep region 132 is preferably between 70 and 100 mm. In one preferred embodiment, the dimension is approximately 90 mm. In the ramp region 134 the lateral dimension diminishes gradually until reaching the shallow region 136. The lateral dimension of the shallow region 136 is preferably between 50 and 80 mm. In one preferred embodiment, the dimension is approximately 65 mm. The ramp region 134 also widens in the transverse direction perpendicular to the lateral direction. The shallow region 136 begins approximately halfway between the first and second holes and continues around the outlet end 128 until reaching the outlet 114. In other embodiments, the ramp region can begin nearer to the inlet 112 and end nearer to the outlet 114 for an even more gradual pressure change. The slope of the ramp region is preferably approximately 0 to 20 degrees. In some instances, the space constraints on the outside of the cover (other vehicle components that must be fitted) will dictate a hump in the ramp or a certain angle. In any case, the cover is optimized to have the least turbulence (e.g., the smoothest flow) through the flow path and to the exit. This will maximize cool air flow with the least resistance to air entering the inlet port for the given constraints.

The cover 110 also includes a high region 138 that extends from the air outlet 114 to the air inlet 112 on an upper side 131 of the cover 110. A portion of the air in the cover moves from the shallow region 136 over the high region 138 and around the driven shaft again before merging with the newly introduced airflow from the air inlet 112. A ridge 140 separates the high region 138 from the deep region 132, the ramp region 134, and the shallow region 136. The ridge 140 extends tangentially from the first hole 122 and reaches approximately to a midpoint of the second hole 124. A portion of the high region 138 at a perimeter of the cover 110 near the air inlet 112 is a divider 142 that directs air passing over the high region 138 back into the main airflow, and prevents the air from exerting outward pressure on the inlet air. The divider 142 covers approximately half the distance between the cover shell 144 and the first hole 122 measured in a radial dimension outward from the first hole 122.

As the air enters the cover 110 from the inlet 112, the laterally width dimensions of the flow path therefrom begin large and become progressively smaller until the air exits the cover 110 at the outlet 114. The effect of this structure is to reduce the pressure drop in the air when introduced to the cover 110 thereby improving efficiency. Conventional designs have an abrupt change in dimension, which causes a larger pressure spike, in turn requiring more pressure to maintain airflow through the cover 110. In some covers, the abrupt dimension change causes the internal air pressure to be large enough to cause air to blow back out of the inlet 112 hindering the efficiency of the cooling system.

FIG. 3 is an isometric view of a portion of a CVT cover 200 according to embodiments of the present disclosure in which the outlet is oriented differently relative to the cover 110. The cover 200 includes features generally similar to features of other covers described herein including the inlet 112, outlet 114, deep region 132, ramp region 134, shallow region 136, high region 138, and ridge 140. The outlet 114 is at approximately the 9 o'clock position relative to the second hole 124. By comparison, the outlet 114 of FIG. 2 is at approximately the 1 o'clock position. The inlet 112 can similarly be oriented differently according to the dimensions of a given CVT. The cover itself can be made using a mold or another suitable manufacturing technique. In some embodiments the cover has a uniform thickness throughout the cover.

In either of these preferred embodiments, the channeling of the cooling air creates less backpressure and more flow through of fresh air to better cool the clutches and belt.

FIGS. 4A-E illustrate various configurations of CVT cover air channeling structures. In FIG. 4A the cover does not include air channeling structures, other than an open, smooth case. In this instance a significant amount of the air flow is recirculated back to the inlet. This recirculated air can create resistance to incoming air such that the flow of cool air into the cover is reduced. The recirculating air is also warmer, thus reducing the clutch and belt cooling.

FIG. 4B shows a slightly modified cover with a diversion wall to direct the air out of the cover near the outlet and driven clutch (not shown in this figure). The wall causes less recirculation and better air flow with less resistance at the inlet and cooler air overall.

FIGS. 4C-E illustrate different structures near the inlet that affect flow. These structures may be used in conjunction with the exit structures discussed above with reference to FIGS. 4A and 4B. FIG. 4C includes only a drop wall from the upper portion of the cover to the lower portion adjacent the inlet. Without a significant diversion for recirculating air flow is not optimized. Thus, incoming air becomes turbulent as it enters the recirculating air flow path.

FIG. 4D includes a recirculating air flow diverter to channel recirculating air above the main inlet flow path. Some turbulence occurs but flow is better than in 4C above.

FIG. 4E includes a larger diverter for the recirculating air. This arrangement puts the recirculating air in a laminar flow path with the entering air to create the best flow with the least resistance. In alternate embodiments, the shield may be larger or smaller to achieve desired flow consistent with packaging and other design parameters.

While the preferred embodiments of the invention have been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiments. For example, the present invention can include other mechanical equivalents that prevent an axle nut from loosening from the axle, including a retaining arm extending from the axle nut to a single lug or to another portion of the wheel. Other embodiments are also possible. Accordingly, the invention should be determined entirely by reference to the claims that follow. 

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
 1. A case for a continuously variable transmission having a drive clutch and a driven clutch held by a drive shaft and a driven shaft respectively, the drive and driven clutches having side faces, the case comprising: an air inlet extending through a first portion of the case; an air outlet extending through a second portion of the case, generally opposite the first portion of the case; and an airflow channel within the case extending between the air inlet and the air outlet.
 2. The case of claim 1, wherein the channel along the airflow path from the air inlet to the air outlet is created by at least one ridge in the case, the ridge restricting the airflow beyond the air outlet.
 3. The case of claim 1, wherein the channel includes a depth defined generally between the side faces of the clutches and the side of the case, the depth of the channel being greater along an airflow path from the inlet to the outlet than along an airflow path from the outlet to the inlet.
 4. The case of claim 3, wherein the depth of the channel is greatest adjacent the air inlet.
 5. The case of claim 4, wherein the depth of the channel is more shallow adjacent the air outlet.
 6. The case of claim 5, wherein the channel includes a ramped portion within the case between the air inlet and the air outlet.
 7. The case of claim 5, wherein the width of the channel is greater at the air outlet than at the air inlet.
 8. The case of claim 1, further comprising a air diverter adjacent the air inlet, the diverter channeling air upstream from the inlet into the flow from the inlet into the channel
 9. The case of claim 1, further including a drive shaft hole and a driven shaft hole, the channel extending adjacent portions of the case forming the holes.
 10. The case of claim 1, wherein the case includes at least two parts that fasten together, the case further comprising bosses for securing the case parts together, the bosses being on an external portion of the case, an interior of the case adjacent the channel being substantially smooth.
 11. A cover for a transmission having a drive shaft and a driven shaft, comprising: a first hole for accommodating one of the drive shaft or the driven shaft of the transmission; a second hole for accommodating the other one of the drive shaft and driven shaft, wherein the cover has a lateral dimension measured in a direction parallel to the shafts, and wherein a line passing between center points of the first and second holes separates the cover into a first side and a second side; an air inlet near the first hole; an air outlet near the second hole; a deep region near the air inlet; a ramp region adjacent to the deep region; a shallow region adjacent to the ramp region, wherein the deep region has a larger lateral dimension than the shallow region and the ramp region slopes between the deep region and the shallow region, wherein the deep region, ramp region, and shallow region are on the first side of the cover, and wherein airflow through the cover is directed to pass into the air inlet, over the deep region, ramp region, and shallow region before exiting the cover; a high region between the air outlet and air inlet on the second side of the cover, wherein the high region has a smaller lateral dimension than the shallow region, wherein a portion of the air from the shallow region passes over the high region before joining the incoming airflow at the inlet; a ridge between the first and second holes and separating the ramp region and the high region; and a diverter between the high region and the air inlet and positioned to prevent air from the high region from exerting pressure on the incoming airflow.
 12. The cover of claim 11 wherein the first hole accommodates the driven shaft and the second hole accommodates the drive shaft.
 13. The cover of claim 11 wherein the diverter has the same lateral dimension as the high region.
 14. The cover of claim 11 wherein the air inlet is at approximately a 3 o'clock position relative to the first hole.
 15. The cover of claim 11 wherein the air outlet is at approximately a 1 o'clock position relative to the second hole.
 16. The cover of claim 11 wherein the air outlet is at approximately a 9 o'clock position relative to the second hole.
 17. The cover of claim 11 wherein the diverter covers a portion of the deep region.
 18. The cover of claim 11 wherein the diverter is a ring segment covering the air inlet and being concentric with the first hole.
 19. The cover of claim 18 wherein the diverter covers approximately half of the deep region as measured in a radial direction relative to the first hole.
 20. The cover of claim 11 wherein the ramp region has a slope less than about 20 degrees.
 21. The cover of claim 11 wherein the lateral dimension of the deep region is between 70 and 100 mm and the lateral dimension of the shallow region is between 50 and 80 mm
 22. The cover of claim 11 wherein the transmission is a continuously variable transmission.
 23. The cover of claim 11 wherein the rotation sense of the drive shaft and driven shaft is such that components of the transmission coupled to the drive shaft and driven shaft move in the same direction as the airflow as the air flows from on the first side of the cover from the air inlet through the deep region, ramp region, shallow region, and to the air outlet.
 24. A cover for a transmission, wherein the transmission includes a drive gear and a driven gear rotatably coupled together, comprising: a first end configured to accommodate the driven gear; a second end opposite the first end configured to accommodate the drive gear; a middle section, wherein the first end, second end, and middle section together form an oval path for airflow; an air inlet; an air outlet opposite the air inlet, wherein air introduced through the air inlet moves around the oval path, and wherein a portion of the air leaves the cover through the air outlet and a portion of the air cycles around oval path; wherein a first portion of the oval path between the air inlet and air outlet is wider near the air inlet and becomes progressively narrower between the air inlet and the air outlet; wherein a second portion of the airflow path between the air outlet and the air inlet is narrower than a narrowest region of the first portion of the oval path; and a diverter extending from the second flow path over the air inlet to prevent air from the second portion of the flow path from exerting pressure onto air introduced to the cover through the air inlet.
 25. The cover of claim 24 wherein the first end is rounded to accommodate the driven gear and the second end is rounded to accommodate the drive gear.
 26. The cover of claim 25 wherein the first portion of the oval path extends from an approximate 3 o'clock position on the first end to an approximate 1 o'clock position on the second end.
 27. The cover of claim 25 wherein the first portion of the oval path extends from an approximate 3 o'clock position on the first end to an approximate 9 o'clock position on the second end.
 28. A transmission, comprising: a drive member; a driven member; means for rotatably coupling the drive member to the driven member to transmit power from the drive member to the driven member; a cover surrounding the drive member and driven member, wherein the cover has an elliptical shape to accommodate the round shape of the drive member and the driven member; an air inlet configured to direct air into the cover to cool the drive member and driven member; an air outlet configured to release air from the cover after cooling the drive member and the driven member; wherein the cover has a lateral interior dimension measured between interior walls of the cover measured in a direction parallel to the axes of rotation of the drive member and driven member; wherein the air inlet and air outlet are positioned to direct the air to circulate around the interior of the cover in an oval path defined by the elliptical shape of the cover, the oval path having a first segment between the air inlet and air outlet on a first side of the cover and a second segment between the air outlet and the air inlet on a second side of the cover; wherein the lateral dimension of the cover on the first side of the cover is widest at the air inlet, narrowest at the air outlet, and ramps from wide to narrow between the air inlet and air outlet; wherein the lateral dimension of the cover on the second side of the cover is narrower than a narrowest point of the first side of the cover; and a diverter extending from the second side of the cover over at least a portion of the air inlet to prevent air moving over the second side of the cover from exerting pressure on incoming air in the air inlet.
 29. The transmission of claim 28 wherein the driven member is a continuously variable clutch.
 30. The transmission of claim 28 wherein the cover includes a hub for accommodating the driven member with a space between the hub and the air inlet, and wherein the air diverter covers approximately half the space between the hub and the air inlet. 